This invention relates to radio systems, and more particularly, to wireless communication apparatus and systems incorporating such apparatus providing a 1:1 facility protection.
The reliability of modern electronic devices has steadily improved as has our dependence on those devices. However, while highly reliable, these devices are not immune from failure resulting from a host of predictable and unpredictable causes and events. Various techniques are used to address the failures inevitable in all systems, and particularly in mission-critical apparatus and systems. For example, certain apparatus and systems incorporate built-in test (BIT) facilities and/or built-in test equipment (BITE) to evaluate apparatus performance, identify impending and actual failures and performance degradation conditions, and isolate, reconfigure and/or bypass around failed or malfunctioning equipment. Such systems may additionally notify appropriate personnel to take corrective action to restore system performance and facilities.
Reliability is a particularly critical issue in communications systems which support multiple users. Failure of a network component at a critical node in a network may disable all communications along the network or severely impede or limit communications along or between segments of the network. Even if a graceful degradation plan is in effect, such failures often limit available bandwidth supported by the remaining network facilities that are still in operation.
One common way to address equipment failures is to provide redundancy on, for example, a 1:1 or 1:n protection basis at the equipment level at communication nodes. For example, a 1:1 or 1:n module protection scheme uses redundant circuit packs within a radio, switching to a standby pack upon detecting failure of an active circuit.
In a xe2x80x9ccoldxe2x80x9d standby configuration, the replacement circuit is not powered until fault detection. Cold standby saves power, wear on the standby and associated circuitry, and the addition of support circuitry required to maintain the redundant standby circuitry in a power-up mode, e.g., additional power supply capacity output terminations such as dummy loads, control circuitry, cooling, etc. Conversely, cold standby requires more time to bring the replacement xe2x80x9con-linexe2x80x9d and risks that the replacement may be inoperative when powered up. Alternatively, the redundant circuitry may be maintained in a xe2x80x9chotxe2x80x9d standby condition so that it can be quickly and automatically substituted for the failed circuit pack or module. To further expedite this transition, the hot standby can be operated in lock-step or an xe2x80x9cerrorlessxe2x80x9d condition so that it works in parallel and synchronously with the operational unit which it backs up. A monitor system can then detect the failure and switch over to the backup unit so that the transition is virtually errorless and transparent to system users.
At a system level, these protection systems may require auxiliary processing equipment to monitor the operational equipment, identify and locate faults, and command appropriate actions to activate and substitute backup equipment for failed units. This means that the redundancy equipment must interface with the equipment being monitored, requires deployment of additional systems, and can create another failure opportunity to bring the system down. Using discrete redundancy control systems also means that additional spares must be kept on hand, increasing costs and complicating logistics.
Accordingly, a need exists for a communication system having high reliability and self-diagnostics. A further need exists for a communication system which automatically reconfigures to replace failed units and maintain network service. A further need exists for communication equipment which incorporates facilities to accomplish network reconfiguration without requiring auxiliary equipment.
The present invention is directed to wireless communication equipment, preferably microwave radio (i.e., 1 GHz and above) equipment, and systems incorporating such equipment, including a method of operating such equipment and systems, which incorporates and integrates built-in test facilities into each radio which, when integrated into a wireless link, such as those of a radio network shown and described in the above referenced patent application entitled xe2x80x9cCOMMERCIAL NETWORK BASED ON POINT TO POINT RADIOSxe2x80x9d, automatically form a system level fault detection and isolation facility. A preferred embodiment of the invention provides built-in test and redundancy control functionality into each active and standby radio in the form of redundancy modules which cooperate to identify faults, reconfigure to replace failed radios, communicate with the rest of the network to identify failed radios in remote nodes, and notify maintenance facilities that a failure has occurred. Preferably, each redundancy module includes a set of rules for identifying and locating failures occurring at the radio module unit, mated radio pair, node and system levels. According to the preferred embodiment, since each redundancy module implements the same rule set and redundancy processing, radio replacement is easily accomplished.
According to one object of the invention, a protection switching method and apparatus is provided wherein the processing to identify a fault and provide appropriate corrective action is incorporated within a radio and is preferably provided within each radio. Further, no auxiliary or external system is required for functioning of the system other than a passive coupler to provide simultaneous inputs to and outputs from the redundant radio pair. Thus, no external control logic is required.
According to one aspect of the invention, minimal network disruption is caused during a changeover by using a hot standby redundancy.
According to another aspect of the invention, a radio communication device, preferably a transceiver although receiver and transmitter circuitry may be utilized discreetly according to the present invention, for use as one of a pair of redundant communication devices forms part of a first communication site. The first communication site is in radio communication with a second communication site of the communication system. The radio communication device, described here with reference to a transceiver embodiment to facilitate discretion of both receive and transmit redundancy, preferably includes a radio transmitter selectively operating in an active and standby mode of operation and a radio receiver. According to a feature of the invention, the radio receiver is also operative in either standby or active modes of operation. The radio transceiver further includes a receiver monitor which is responsive to the radio receiver to detect a failure of a transmitter of a pair of remote transceivers located at the second communication site. The radio transceiver also includes a controller which controls the radio transmitter to operate in the active and standby modes of operation in response to the pair of remote transceivers detecting a failure of one of the pair of redundant radio transceivers. The controller is also responsive to the receiver monitor and to a similar signal received from a receiver monitor of the other radio transceiver of the pair of redundant radio transceivers so as to supply a transmitter failure signal to the remote pair of radio transceivers located at the second communication site. Accordingly, the controller preferably includes facilities for detecting a local transmitter failure in response to a remote site""s loss of signal and to identify a local receiver failure in response to only one of the local receivers experiencing a loss of signal. Conversely, the controller provides a remote transmitter failure signal in response to a loss of received signal by both local receivers.
According to a feature of the invention, a preferred embodiment radio receiver or transceiver includes an output for selectively providing a signal from the radio receiver in response to (i) a receiver monitor and/or (ii) a signal from the receiver monitor of the other transceiver of a redundant pair.
According to another feature of the invention, a preferred embodiment radio transmitter or transceiver includes a transmitter monitor for detecting an output of the transmitter, the controller being responsive to the transmitter monitor for providing a control signal to the other of a redundant pair.
According to another feature of the invention, a preferred embodiment transmitter of transceiver includes a dummy load selectively attenuating or terminating an output of the radio transmitter when the transmitter is operated in the standby mode of operation, i.e., the radio transmitter operating in standby node is not RF transmitting.
According to another aspect of the invention, a radio transceiver system for use at a communications node of a radio communications system preferably includes first and second radio transceivers, although it shall be appreciated that the aspects of the present invention described may be utilized in conjunction with a received and/or transmitter system for use at a communications node rather than a transceiver, if desired. Each of the radio transceivers includes a radio transmitter selectively operable in standby and active modes of operations and a radio receiver. Also included as part of each radio transceiver is a controller which is preferably operative to monitor the receiver and, in response, provide a receiver status indicator. The preferred embodiment controller also provides a remote transmitter failure signal responsive to the receiver status indicator and to the receiver status indicator of the other transceiver of the pair. The preferred embodiment controller is also operative to control the transmitter to selectively operate in the standby and active modes of operation in response to a remote transmitter failure signal received from an associated remote redundant radio transceiver system.
According to a feature of the invention, the preferred embodiment controllers of the first and second radio transceivers forming the pair are in communication to operate one of the controllers in a master mode for providing the remote transmitter failure signal, while the other controller is operated in a slave mode for providing a respective receiver status indicator to the controller which is being operated in the master mode.
According to another feature of the invention, the preferred embodiment receiver status indicators include a loss of signal condition. One of the controllers of the pair of radio transceivers receives the receiver status indicator of the other radio transceiver and, in response to the received indicator and the indicator of that transceiver (i.e., the receiver status indicators of both the first and second transceiver), the controller determines the type of failure according to application of a predetermined rule. According to this aspect of the invention, the controller may determine that there has been a failure of the transmitted signal in response to the receiver status indicators of both remote radio transceivers indicating that there was a loss of signal, i.e., both indicating a loss of signal condition. On the other hand, the controller would determine that there had been a failure of a local receiver associated with one of the local radio transceivers and, in particular, the transceiver corresponding to the loss of signal indicator, if the status indicator of one of the transceivers does not indicate a loss of signal.
According to another aspect of the invention, a communication system includes a plurality of nodes. At least one of the nodes includes first and second pair of redundant radio transceivers (although radio receivers and/or transmitters may be utilized if desired) in radio communication with respective remote nodes of the system, i.e., a previous node and a subsequent node of a network as shown and described in the above referenced patent application entitled xe2x80x9cCOMMERCIAL NETWORK BASED ON POINT TO POINT RADIOSxe2x80x9d. Each of the pair of redundant radio transceivers preferably includes a transmitter selectively operable on a standby and an active mode of operation and a receiver. According to a feature of the invention, the receiver may likewise be operable in either an active or standby mode. The radio transceiver also preferably includes a controller operative in master and slave modes to selectively (a) monitor the receiver portion of the radio transceiver and, in response, provide a receiver status indicator, and (b) provide a remote transmitter failure signal in response to the receiver status indicator and to a receiver status indicator of the other one of the pair of redundant radio transceivers. The controller further (c) controls the operating modes of the transmitters of the pair of redundant radio transceivers to selectively operate in the standby and active modes in response to a remote transmitter failure signal provided by an associated one of the previous and/or subsequent nodes.
According to a feature of the invention, one of the pair of redundant radio transceivers is preferably selectively operated in an active mode of operation while the other one of the pair is operated in a standby mode of operation. The xe2x80x9cactivexe2x80x9d transceivers of each pair of radio transceivers are connected to communicate data such as between a previous and a subsequent relay node of the communication system or between a previous subsequent relay node and a termination device coupled to the active transceiver.
According to another aspect of the invention, a method of operating a radio communication network is described where the network includes a plurality of nodes, each node including first and second pairs of radio transceivers wherein one radio transceiver of each of the pairs is operated in an active mode and the other in a standby mode. The method preferably includes the steps of identifying signals transmitted to ones of the first and second pairs of transceivers and determining an operational status of a receiver portion of each of the transceivers of the first and/or second pairs of radio transceivers in response to a dissimilarity of signals identified by the respective pairs of radio transceivers. That is, a loss of signal indicator from only one of the receivers of a redundant pair is indicative of a failure of that receiver rather than a failure of the associated remote transmitter to transmit a signal. The method further includes determining an operational status of a remote node (i.e., the remote transmitter) in response to a failure to receive a signal from the remote node by an associated one of the pair of transceivers, and selectively changing the operating mode of one of the pair of transceivers in response to such determination. That is, as a consequence of determining a failure at either the remote transmitter, or one of the local receivers, the appropriate backup transceiver, or portion thereof, will be preferably activated and substituted for the failed unit identified according to the method.
According to another aspect of the invention, a method of operating a radio communications network is provided for the operation of first and second terminal nodes and an intermediate relay node (although referenced herein as a xe2x80x9crelay nodexe2x80x9d, it shall be appreciated that such a node may in fact not only provide throughput of data as between a series of links in a network, but may also identify and direct data to termination equipment coupled thereto). The first and second terminal nodes each include a pair of radio transceivers while the relay node comprises two (back-to-back) pairs of radio transceivers. One radio transceiver of each of the pairs is operated in an active mode while the other is maintained in a standby mode (preferably a hot standby mode). Another aspect preferably includes the steps of detecting an alarm condition caused by a loss of signal by one radio transceiver of the pair and interrogating the other radio transceiver of the pair to identify a corresponding loss of signal by the other radio transceiver. A preferred embodiment of the method then applies a predetermined rule to determine whether a receiver or transmitter failure has most likely occurred and switches operation modes of one of the pairs of radio transceivers in response to the determination. According to a feature of the invention, the method also includes the step of transferring control of one of the pair of transceivers, e.g., redesignating to the active transceiver the master control function for the pair.
These, together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described in the claims, with reference being had to the accompanying drawings forming a part thereof, wherein like numerals refer to like elements throughout.